Skeletal morphoanatomy of the Brown Skua Stercorarius antarcticus lonnbergi and the South Polar Skua Stercorarius maccormicki

Abstract

The Brown Skua Stercorarius antarcticus lonnbergi and the South Polar Skua Stercorarius maccormicki, which breed sympatrically in the Southern Hemisphere, are difficult to identify in the field because of their similar coloration and external morphology. Although several morphological and biological aspects have been previously discussed, no data have been published about their skeletal anatomy. In this paper we make a comparative description of the cranial and appendicular skeleton of both skua species. As a result, and although the differences are small, it has been found that some characters of the skull and the thoracic and pelvic limbs, allow the distinction between S. antarcticus lonnbergi and S. maccormicki.